38 CALIFORNIA ACADEMY OF SCIENCES. 



some of the schemes of tunicate classification recognized 

 at present, place it in a different family from that to which 

 the genus Perophora is assigned ; or, by other schemes, in 

 a different suborder. The character to which I refer is 

 this: /;/ very many, though not all, of the eolonies the 

 asccdiozooids are as completely imbedded in a common test 

 as they are in Botryllus or Goodsiria. 



The distinction between " simple " and " compound," 

 as applied to Ascidians, the importance of which has 

 diminished in the same ratio that our knowledge of the 

 group has increased, is reduced to ;/// by the discovery of 

 this form, so far as its value in determining affinities is 

 concerned. 



Down to Savigny's time ('16) the compound Tunicates 

 had not been distinctly recognized as Tunicates, but had 

 been generally regarded as Alcyonaria. This author 

 made clear their true nature, and grouped them together 

 under the name Tcthys coniposces, as opposed to the Tcthys 

 simples.'^ 



After this Lister ('34) made the first of the long series 

 of discoveries that has finally resulted in establishing a 

 most perfect gradual transition from the one group to the 

 other. It is an interesting fact that his discovery was 

 that of the first Perophora known to science. In it he 

 showed that the ascidiozooids of a colony are all con- 

 nected together by stolons, through which the blood flows 

 constantly and regularly from one to another. Clavelina 

 was known to Savigny, but he seems not to have been 

 aware that it reproduces by gemination, and he placed it 

 among his Tcthys simples. The discovery of this latter fact 

 was made by Milne-Edwards ('42). This author invest- 

 igated this and its allied forms in his usual careful manner, 



* I have not had access to any of Savigny's original works, bnt take this 

 from Jones ('48, pp. 5 and 7). 



